The invention relates to a method and a device for governing of a rotor diameter. Devices of this type are used to prevent a jamming of the sluice rotor in the case when during the startup of a system the hot bulk material heats the rotor up faster than the case and said rotor then touches the case beyond its diameter enlargement.
In accordance with the state of the art a compromise of preheating of the case and production of a larger radial gap at about 20° Celsius manufacturing temperature is selected in order to obtain a below operating temperature which excludes a contact of the rotor on the case.
The price for this is higher leakage values in the starting up phase until ultimately the pre-calculated operating gap is formed from the production gap by means of the complex process of the case pre-heating and the thermal expansion of the rotor. References to this are to be found in the publication “Powder handling & processing: Minimum gas leakage through rotary feeders used in (hot) Dense Phase Pneumatic Conveying Systems”, Vol. 15, No. 1, January/February 2003.
In DE 37 42 519 and in DE 37 42 521 controlled plastic strips are used in order to make the rotor diameter changeable. Further the most varied webs adjustment options have become well known, from spring contacts to the application of pneumatic or hydraulic auxiliary energy.
All of these solutions are built on web grooves which are difficult to manufacture, and their radial alteration. If one mills the finished cellular wheel by means of the assistance of a side and face milling cutter, one always finds buckled webs caused by welding. When the web is milled, the area buckles when welding takes place on the web. In the case of the cellular wheel sluice sizes in demand on the market of 500 to 800 diameters this is an expensive, pointless underpinning.
Another method of solution attempts to achieve optimum operating cracks by means of temperature-dependent shifting of a conical rotor in the tapered case diameter with the help of an adjustment device.
DE 199 36 136 describes the most variable solutions in which resources for measurement of the distance between the cellular wheel and the case bore are present and the cellular wheel and/or the case bore is radially deformable at least locally in dependency on the measured value.
DE 11 74 257 also builds on the web grooves in which by means of a directional solution plates corresponding to the radial and axial cellular wheel wall length made of different, thermally expansible plastics were proposed.
The plastics are arranged in such a way that the introduced temperature can perform a diameter compensation of the cellular wheel in dependency on the temperature. In similar fashion the selection of the material for the case to the cellular wheel material can have an influence on the dimension of the operating gap.
This solution has not gained acceptance in practice. It is known that the temperature expansion takes place three-dimensionally. Unfortunately DE 11 74 257 does not give any information about the effect of plate expansion in an axial direction, in particular the effect on the fastening screws Items 6 and 7, which are exposed to impermissible tensions over the length of the plate connections, is not given.
The plates of higher thermal expansion expand in all three space axes with the appropriate heat action. For this reason, in the case of the cited publication the disadvantage of an unavoidable bimetallic effect existed, which results from the fact that the displacement body extends over the entire axial length of the cellular wheel web and due to its great expansion caused by the heat, bulges between the fastening screws.
Consequently the functionality of the expansion device would no longer be given, because the discarding of the displacement bodies in the very narrow clearing of the cellular wheel web lead to too high friction values at the web groove wall, which prevented a compensating movement.
The unavoidable bimetallic effect resulting in axial direction can also jeopardize the movement in the web groove in radial direction, as well as the penetration of the bulk material into the plate sandwich slot combination. The cause for the susceptibility for failure is the fact that plate Item 3 is in one piece. The jamming effects that as appear a result made the device unusable.